Neafie, Levy & Co., commonly known as Neafie & Levy, was a Philadelphia, Pennsylvania shipbuilding and engineering firm that existed from the middle of the 19th to the beginning of the 20th century. Described as America's "first specialist marine engineers", Neafie & Levy was probably the first company in the United States to combine the building of iron ships with the manufacture of steam engines to power them. The company was also the largest supplier of screw propellers to other North American shipbuilding firms in its early years, and at its peak in the early 1870s was Philadelphia's busiest and most heavily capitalized shipbuilder.

USS Alligator, the fourth United States Navy ship of that name, is the first known U.S. Navy submarine, and was active during the American Civil War. During the Civil War the Confederate States Navy would also build its own submarine, H. L. Hunley.